The start of a run can feel like a fight against your body – and that is normal
This sensation is actually caused by a normal feature of human physiology.
Black News 
Many runners describe the first ten to 15 minutes of a run as the hardest of all. Breathing can feel laboured, the legs can feel heavy and a pace that would normally seem manageable may suddenly feel surprisingly difficult.
It might be easy to assume the reason your run feels so difficult at the start is because you’re not fit enough. But in reality, this sensation is actually caused by a normal feature of human physiology – and one that affects almost everyone, from someone attempting their first 5K to elite endurance athletes.
One way I often explain this phenomenon to athletes and students is that when you begin running, an argument starts between your muscles and your cardiorespiratory system. While there’s nothing we can do to stop this quarrel from happening, there are many things we can do to help the body find a resolution more quickly in the future.
The moment you start running, your working muscles demand a rapid supply of energy almost instantly. Yet the system responsible for producing that energy from oxygen cannot respond quite as quickly.
To meet this increased demand, your heart rate rises, breathing becomes deeper and faster and blood flow is redirected towards the working muscles. These adjustments allow more oxygen...
